Understanding when income tax and capital gains tax (CGT) are due is essential for planning your finances and avoiding unnecessary penalties. Both taxes operate under defined UK deadlines, and missing these can result in interest, penalties, and avoidable administrative charges.
If you are required to file a Self Assessment tax return, the timing of your income tax payments depends on the tax year and the Self Assessment filing process.
The UK tax year runs from 6 April to 5 April the following year.
Paper returns: due by 31 October following the end of the tax year
Online returns: due by 31 January following the end of the tax year
Filing after these dates may trigger automatic penalties, even if no tax is due.
Most self-employed individuals and some landlords must make payments on account toward the next year’s tax bill.
For a given tax year:
31 January – first payment on account is due
31 July – second payment on account is due
31 January (following year) – balance of tax owed for the year, plus first payment on account for the next tax year
Payments on account are based on your previous year’s tax bill and aim to spread the burden of income tax and Class 4 National Insurance contributions over the year.
If your income is expected to fall significantly, you can apply to reduce payments on account — but only if there is a realistic basis for doing so.
For self-employed individuals, National Insurance contributions are due alongside income tax in Self Assessment.
Class 4 National Insurance is payable on profits above the statutory thresholds and is collected at the same time as income tax.
For employed individuals, National Insurance is generally collected through PAYE, but additional payments may be due through Self Assessment if you have other sources of income.
Capital Gains Tax (CGT) is payable when you dispose of an asset and realise a gain. The timing of reporting and payment depends on the type of asset and whether the gain arises on residential property or other assets.
Where a capital gain arises on the sale of UK residential property that does not qualify entirely for private residence relief, a CGT return must normally be submitted, and payment made within 60 days of completion.
This applies even if the gain is fully covered by other reliefs or taper relief — reporting is required unless the gain is exempt.
For other chargeable assets, CGT is usually due by 31 January following the end of the tax year in which the gain arose.
For example:
A gain arising in the tax year ending 5 April must be reported and paid by 31 January following that tax year.
Every taxpayer has an annual exempt amount for CGT, which may reduce or eliminate the chargeable gain. Utilising this exemption effectively — for example, by planning disposals across tax years or between spouses — can result in significant tax savings.
Whether it is income tax or CGT, reporting must be accurate, complete, and submitted by the relevant deadline. A late return may attract:
Automatic penalties
Interest on late payments
Additional compliance charges
To avoid cash flow surprises and penalties:
Monitor income and gains throughout the year
Maintain accurate records of all income and disposals
Forecast your tax liabilities well before deadlines
Consider spreading disposals across tax years when appropriate
Use available allowances and reliefs efficiently
Tax deadlines and liabilities can be complex, particularly when you have multiple income sources or investment disposals.
Applegrow Financial Advisors can help you:
Identify all deadlines that apply to your tax situation
Prepare accurate tax returns and forecasts
Plan payments to minimise cash flow stress
Ensure you comply with all UK tax obligations
If you want clarity on when your income tax or capital gains tax payments are due — and how to manage them — Applegrow is here to provide clear, personalised guidance.
Contact Applegrow Financial Advisors for tailored support and confidence with your UK tax obligations.
